Since 2015, when we first reported that the half-Heusler alloy NbCoSb with a nominal 19-valence-electrons composition exhibits the moderate thermoelectric properties of a heavily doped n-type semiconductor, we have been studying the preparation of pure-phase materials. Here we report, for the first time, the effects of Nb and Sb deficiencies on the phase composition and thermoelectric properties of NbCoSb. The experimental results show that phase-pure material can be achieved if the composition is slightly Nb and Sb deficient and that intrinsic vacancy defects have a remarkable effect on the thermoelectric performance. The ZT value is doubled and a maximum ZT of 0.8 is achieved in Nb_0·97CoSb_0.99 at 973 K, benefiting from the elimination of impurity phases and the optimization of carrier concentration. This work proves that introducing vacancy defects is an effective strategy to improve the thermoelectric properties of some half-Heusler alloys, especially of nominal 19-electron half-Heusler compounds.

自 2015 年以来，当我们首次报道具有标称 19 价电子组成的半赫斯勒合金 NbCoSb 表现出重掺杂 n 型半导体的中等热电特性时，我们一直在研究纯相材料的制备。在这里，我们首次报告了 Nb 和 Sb 缺陷对 NbCoSb 的相组成和热电性能的影响。实验结果表明，如果成分略有 Nb 和 Sb 不足，则可以实现相纯材料，并且本征空位缺陷对热电性能有显着影响。ZT 值加倍，在 Nb _{0 · 97} CoSb _{0.99 中}达到最大 ZT 为 0.8在 973 K 时，受益于杂质相的消除和载流子浓度的优化。这项工作证明，引入空位缺陷是改善某些半赫斯勒合金，尤其是标称 19 电子半赫斯勒化合物的热电性能的有效策略。